Engine Oil Flow Control Between FOHE and AOHE Heat Sinks
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Solution Overview
Problem
Conventional Thermal Management Systems (TMS) in engines face challenges in managing oil temperature and flow rates, leading to reduced engine component life and thermal efficiency, particularly due to mechanical oil pumps that are proportional to engine rotational speed, limiting the ability to optimize parameters other than Specific Fuel Consumption (SFC).
Innovation Solution
The implementation of an electrical TMS with oil pumps decoupled from engine rotational speed, allowing independent control of oil flow to Fuel Oil Heat Exchanger (FOHE) and Air Oil Heat Exchanger (AOHE), enabling flexible oil mass flow rates to minimize SFC or average oil temperature, with control functions optimizing for specific flight conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a mechanical positive displacement oil pump driven by engine shaft is used, then the oil flow is proportional to engine rotational speed, but the ability to independently control oil mass flow rate is limited
Solution Approach 1:
The patent replaces the mechanical positive displacement pump driven by engine shaft with an electrically driven variable speed pump. This substitution allows the pump to be controlled independently from engine rotational speed through electrical controls, enabling independent adjustment of oil mass flow rate to optimize thermal management while maintaining simpler overall control architecture through electronic control systems.
Solution Approach 2:
The patent implements a variable speed pump that can dynamically adjust its rotational speed to control oil mass flow rate. This dynamic capability allows the system to adapt oil flow conditions in real-time based on thermal management requirements, rather than being constrained to a fixed mechanical relationship with engine speed.
2Use of energy by moving object
If heat is transferred primarily to fuel before combustion, then thermal efficiency and specific fuel consumption are improved, but the maximum allowable temperature of fuel limits the maximum heat transfer amount
Solution Approach 1:
The patent introduces an oil-to-fuel heat exchanger as an intermediary device that transfers heat from the engine oil to the fuel before combustion. This intermediary system allows thermal energy to be transferred to the fuel without directly exposing the fuel to excessive temperatures, as the heat exchanger mediates the thermal transfer process and controls the temperature of fuel entering the combustion chamber.
Solution Approach 2:
The patent utilizes parameter changes by controlling the mass flow rate of oil through the heat exchanger to optimize heat transfer. By adjusting oil flow parameters, the system can maximize heat transfer to fuel within safe temperature limits, thereby improving thermal efficiency while respecting fuel temperature constraints.
3Temperature
If the remaining heat is transferred into bypass air, then heat management is achieved, but engine thermal efficiency is reduced
Solution Approach 1:
The patent converts the previously wasted heat in bypass air into a useful resource by capturing it through heat exchangers and transferring it to the fuel. This approach transforms what was previously a harmful waste heat into a beneficial thermal energy source that improves engine thermal efficiency and reduces fuel consumption.
4Duration of action of stationary object
If oil temperature is reduced to improve component life, then design life is extended, but the ability to manage excess heat efficiently is reduced
Solution Approach 1:
The patent implements dynamic control of oil mass flow rate through an electrically driven variable speed pump. This allows the system to maintain optimal oil temperature for component life by adjusting flow rates in real-time, while simultaneously managing excess heat efficiently by directing appropriate amounts of heat to the fuel heat sink based on operational conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach extends engine component life by maintaining optimal oil temperatures and improves thermal efficiency by allowing heat transfer primarily to the fuel sink, while minimizing penalties on SFC, and reduces complexity in control systems by maintaining a constant combined total oil mass flow rate.
Implementation Method 1
a fuel oil heat exchanger configured to receive a portion of the oil from the engine and transfer heat from the oil to the fuel
Implementation Method 2
an air oil heat exchanger configured to receive the remaining oil from the engine and transfer heat from the oil to the bypass air
Data Source
AI summary
A method of controlling the oil flow in an engine is provided. In preferred embodiments, the method comprises: flowing oil to a first oil pump upstream or downstream of a fuel oil heat exchanger and flowing oil to a second oil pump upstream or downstream of an air oil heat exchanger. One of two control functions to control the oil mass flow rate through the first oil pump is selected wherein the first control function minimizes specific fuel consumption (“SFC”) by the engine and the second control function minimizes average oil temperature. Preferably, the oil pumps are electric and the total combined oil mass flow rate of the first and second oil pumps is maintained constant.